The present invention relates to an apparatus for controlling a power transmission device, which is provided with a lock-up mechanism in a torque converter secured between a prime mover and a speed changer.
As such a power transmission device, there is, for example, such a construction that the power of a prime mover, which is inputted via a torque converter, is transmitted by a belt-type step-free reduction mechanism consisting of a drive-side pulley, a driven-side pulley and a belt member suspended over both the pulleys, or by a forward and rearward changer mechanism consisting of friction engagement elements. Such a power transmission device has been employed for vehicles, etc. In such a power transmission device, the speed changer is operated by utilizing line pressure that is obtained by regulating working oil pressure provided from a hydraulic pump, and engagement control of the lockup mechanism is carried out by utilizing surplus oil produced when regulating the pressure. Herein, where a load is large and the number of output revolutions of the speed changer (a vehicle speed is low where the speed changer is applied to the vehicle) is small (at this time, the lockup is not carried out), or where the speed is quickly reduced from a constant (high-speed) running state, it is necessary to provide a large capacity of working oil of high pressure in order to operate the speed changer. Therefore, the power transmission device is constructed so that at least such working oil can be supplied to the speed changer.
On the other hand, in such a power transmission device, although the lockup is performed between the prime mover and speed changer where the load of the speed changer is small and the number of output revolutions of the speed changer, is large, no high-pressure working oil is required to operate the speed changer in such situations, and since the frequency of speed reduction is low, no large capacity of working oil is required. Therefore, in such situations, if the line pressure is retained at a high-pressure level or a large capacity of working oil is continuously supplied, such a problem occurs, where the loss of power will become remarkable, and the fuel consumption will be increased.
Further, in such a power transmission device for a vehicle, in order to prevent an excessive torque from being inputted onto a belt or to relieve a shock occurring when changing the mode from neutral to drive or changing from forward drive to rear drive, it is necessary to control the engagement capacity of friction engagement elements (forward drive clutch or rearward drive brake) that constitute the forward and rearward changer mechanism. Engagement capacity control of such friction engagement elements is carried out by controlling the oil pressure provided to the friction engagement elements. However, a linear solenoid valve is frequently used where it is necessary to carry out the oil pressure control at high accuracy. In addition, in the lockup mechanism of a torque converter, it is preferable that engagement capacity control optimal for the vehicle velocity, etc., is performed. The linear solenoid valve is also frequently used for these purposes.
Actually however, such linear solenoid valves are generally expensive, and if two linear solenoid valves are used as described above, another problem occurs, where the construction increases the cost thereof.
It is therefore an object of the invention to provide an apparatus for controlling a power transmission device, which adjusts the pressure or supply quantity of working oil used for operation a speed changer in compliance with operation control of a lockup mechanism in response to a load, and which is devised so as to improve the fuel consumption by decreasing the loss of power.
Also, it is another object of the invention to provide an apparatus for controlling a power transmission device, which enables engagement capacity control of friction engagement elements and engagement capacity control of the lockup mechanism by means of a single linear solenoid valve.
A first aspect of the invention is an apparatus for controlling a power transmission device that is provided with a lockup mechanism for connection and disconnection between a prime mover (for example, an engine in an embodiment) and a speed changer (for example, a step-free speed changer, CVT, in the embodiment) in response to supply and discharge of working oil in a torque converter secured between the prime mover and the speed changer, wherein the apparatus comprises a lockup changing means (for example, a lockup shift valve 190 in the embodiment) that causes the lockup mechanism to change the position thereof between the first position (for example, the lockup mechanism operating position in the embodiment) where the lockup mechanism supplies and discharges the working oil so as to carry out the connection and the second position (for example, the lockup mechanism non-operating position in the embodiment) where the lockup mechanism supplies and discharges the working oil so as to carry out the disconnection; a working oil pressure changeover setting means (for example, a regulator valve 110 in the embodiment) that is capable of changing the pressure setting state thereof to the first state (for example, a state corresponding to low pressure in the embodiment) where the pressure of working oil used to operate the speed changer is set to the first pressure (for example, low line pressure in the embodiment) and to the second state (for example, a state corresponding to high pressure in the embodiment) where the pressure of working oil used to operate the speed changer is set to the second pressure (for example, high line pressure in the embodiment), which is higher than the first pressure; and a signal pressure outputting means (for example, an electrical control unit and first solenoid valve 150 in the embodiment) for selectively outputting any one of the first signal pressure by which the lockup changing means is positioned at the first position and the working oil pressure changing means is made into the first state and the second signal pressure by which the lockup changing means is positioned at the second position and the working oil pressure changing means is made into the second state.
The apparatus for controlling a power transmission device according to the first aspect of the invention is constructed so that a mode where the lockup mechanism is made into an operating state (a state where the output shaft of a prime mover is connected to the input shaft of a speed changer), and the pressure (line pressure) of working oil used to operate the speed changer is set to low pressure level, and a mode where the lockup mechanism is made into a non-operating state (a state where the prime mover is disconnected from the speed changer), and the pressure of the working oil is set to a high pressure level are changed over by changing the outputs of two types of signal pressure, which are the first signal pressure and second signal pressure. Therefore, the latter mode is selected where the load is large and the number of output revolutions of the speed changer (the running speed of a vehicle in which the power transmission device is incorporated) is small, and the former mode is selected where the load is small and the number of output revolutions thereof is large, whereby the fuel consumption can be decreased by lowering the loss of power. In addition, the output of the signal pressure can be changed over by, for example, only an ON-OFF controllable single solenoid valve and control device thereof, and the construction thereof can be simplified.
Also, a second aspect of the invention is an apparatus for controlling a power transmission device that is provided with a lockup mechanism for connection and disconnection between a prime mover (for example, an engine in an embodiment) and a speed changer (for example, a step-free speed changer, CVT, in the embodiment) in response to supply and discharge of working oil in a torque converter secured between the prime mover and the speed changer, wherein the apparatus comprises a lockup changing means (for example, a lockup shift valve 190 in the embodiment) that causes the lockup mechanism to change the position thereof between the first position (for example, the lockup mechanism operating position in the embodiment) where the lockup mechanism supplies and discharges the working oil so as to carry out the connection and the second position (for example, the lockup mechanism non-operating position in the embodiment) where the lockup mechanism supplies and discharges the working oil so as to carry out the disconnection; a capacity-changing type hydraulic pump that supplies working oil used to operate the speed changer at the first capacity (for example, a small capacity in the embodiment) or at the second capacity (for example, a large capacity in the embodiment) that is greater than the first capacity; a capacity changing means (for example, a discharge capacity changing valve 101 in the embodiment) that causes the hydraulic pump to be changed between the first position (for example, a position corresponding to the small capacity in the embodiment) where working oil is supplied to the hydraulic pump at the first capacity and the second position (for example, a position corresponding to the large capacity in the embodiment) where working oil is supplied to the hydraulic pump at the second capacity; and a signal pressure outputting means (for example, an electrical control unit and first solenoid valve 150 in the embodiment) for selectively outputting any one of the first signal pressure, by which the lockup changing means is positioned at the first position and the capacity changing means is positioned at the first position, and the second signal pressure, by which the lockup changing means is positioned at the second position and the capacity changing means is positioned at the second position.
The apparatus for controlling a power transmission device according to the second aspect of the invention is constructed so that a mode where the lockup mechanism is made into an operating state (a state where the output shaft of a prime mover is connected to the input shaft of a speed changer), and the working oil used to operate the speed changer is supplied at a small capacity from the hydraulic pump, and a mode where the lockup mechanism is made into a non-operating state (a state where the prime mover is disconnected from the speed changer), and the working oil is supplied at a large capacity from the hydraulic pump are changed over by changing the outputs of two types of signal pressures. Therefore, the latter mode is selected where the load is large and the number of output revolutions of the speed changer (the running speed of a vehicle in which the power transmission device is incorporated) is small, and the former mode is selected where the load is small and the number of output revolutions thereof is large, whereby the fuel consumption can be decreased by lowering the loss of power. In addition, the output of the signal pressure can be changed over by, for example, only an ON-OFF controllable single solenoid valve and control device thereof, and the construction thereof can be simplified.
A third aspect of the invention is an apparatus for controlling a power transmission device that is provided with a speed changer (for example, a step-free speed changer, CVT, in the embodiment), which changes power inputted from a primer mover (for example, an engine in the embodiment) and outputs the same; a torque converter that is secured between the output shaft (for example, a crankshaft Es in the embodiment) of the prime mover and the input shaft (for example, an input shaft 20 in the embodiment) of the speed changer and transmits power; and a lockup mechanism that transmits power between the output shaft and the input shaft at an engagement capacity in response to supplied oil pressure; wherein the apparatus comprises: friction engagement elements (for example, forward clutch 65 and rearward brake 66 in the embodiment) that transmit power in the speed changer at an engagement capacity in response to the supplied oil pressure; a linear solenoid valve (for example, a linear solenoid valve 130 in the embodiment) for producing control pressure by regulating line pressure; a first change valve (for example, a clutch shift valve 150 in the embodiment) having the first position where the control pressure is supplied to the friction engagement elements and the second position where the line pressure is supplied to the friction engagement elements; a second change valve (for example, a lockup shift valve 170 in the embodiment) having the first position where the control pressure is supplied to the lockup mechanism and the second position where supply of the control pressure to the lockup mechanism is interrupted; and a signal pressure outputting means (for example, a solenoid valve 140 in the embodiment) for selectively outputting any one of the first signal pressure (for example, OFF signal pressure in the embodiment) by which the first change valve is positioned at the first position and the second change valve is positioned at the second position and the second signal pressure (for example, ON signal pressure in the embodiment) by which the first change valve is positioned at the second change position and the second change valve is positioned at the first position. The control pressure supplied to the friction engagement elements and lockup mechanism includes control pressure produced by the linear solenoid valve and those (for example, engagement capacity control pressure of the lockup mechanism 50, which is obtained by being converted by a lockup control valve 180, in the embodiment) obtained by converting (for example, amplifying) by means of other valves.
In the apparatus for controlling a power transmission device according to the third aspect of the invention, since the first change valve is positioned at the first position by the signal pressure outputting means, and the second change valve is positioned at the second position, it is possible to control an engagement capacity of the friction engagement elements by using the control pressure produced by the linear solenoid valve. At this time, although the engagement capacity of the lockup mechanism cannot be controlled by using the control pressure, the engagement capacity of the friction engagement elements is controlled when amplifying the torque by means of the torque converter (if the control device is for a vehicle, when starting the vehicle), wherein since the lockup mechanism is not operated in such a situation, there is no disadvantage. On the other hand, since the first change valve is positioned at the second position by the signal pressure outputting means, and the second change valve is positioned at the first position, it becomes possible to control the engagement capacity of the lockup mechanism by using the control pressure produced by the linear solenoid valve. At this time, the line pressure is supplied to the friction engagement elements, thereby causing a completely engaged state to be maintained, wherein, although no engagement capacity control can be performed, since the engagement capacity of the lockup mechanism is controlled when the output of the prime mover is stabilized and the torque is not amplified by the torque converter (that is, when a vehicle runs at a high speed if the control device is employed in the vehicle), the engagement capacity control of the friction engagement elements is not required in such a situation. That does not constitute any problem.
As described above, in the apparatus according to the third aspect of the invention, it is possible to change an object to be controlled by control pressure produced by the linear solenoid valve to any one of the friction engagement elements and the lockup mechanism, wherein both engagement capacity control of the friction engagement elements and engagement capacity control of the lockup mechanism can be carried out by means of a single linear solenoid valve. Therefore, the apparatus for controlling a power transmission device according to the invention does not require two linear solenoid valves as in the related arts, wherein the production costs thereof can be remarkably reduced.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.